Adjustable contact pressure switch mechanism



Nov. 16, 1965 G. E. GAUTHIER 3,218,428

ADJUSTABLE CQNTACT PRESSURE SWITCH MECHANISM Filed Dec. 19, 1965 FIQZ FIGH- INVENTOR. Game: 5. GflurH ER BY @M 9 FIG. 3

ATToR/vey United States Patent 3,218,428 ADJUSTABLE CONTACT PRESSURE SWITCH MEOHANISM George E. Gauthier, Plainville, Conn., assiguor to General Electric Company, a corporation of New York Filed Dec. 19, 1963, Ser. No. 331,714 6 Claims. (Cl. 200-170) This invention relates to contact structures for electrical switching mechanisms and more particularly to switching mechanisms having spring-biased switch con tacts.

In operation of circuit breakers it is, of course, necessary to obtain proper contact pressure between the stationary and the movable contacts. In circuit breakers having toggle-operated contact arms, the contact arm has a limited movement toward the stationary contact. A variation of relatively small extent in the length of the required stroke due to even slight wear of the contact forces can therefore detract substantially from proper contact pressure.

Accordingly it has become common to mount the movable contact on the contact-carrying arm so that it is movable with respect thereto and to spring bias the movable contact away from the contact-carrying arm and to ward the stationary contact. This spring bias is provided in an attempt to maintain adequate contact pressure even though the length of the stroke of the movable contact-carrying arm may vary slightly.

In those circuit breakers having compound contact structures including both main and arcing contacts I have found it to be especially important to provide an easily adjustable arrangement for varying not only the absolute contact pressures, but also the relative contact pressures as between main contacts on the one hand and arcing contacts on the other hand. For example, in a typical compound contact structure having both main and arcing contacts if the arcing contact pressure is too great because of the spring bias provided, the result upon the main contact may be an undesirable reduction in contact pressure. This can lead to bouncing or chattering of the main contacts under high current conditions and, consequently, to erosion of the contacts. If, however, the spring bias on the arcing contacts is too low, the inertia of the arcing contacts during switch closing operations may result in the arcing contacts being closed too late to protect the main contacts, or the arcing contacts may bounce excessively. It is clear from these examples alone that the consequences of imperfectly adjusted contact pressure can be serious.

This invention contemplates the construction of a circuit breaker mechanism in which the contact structure is provided with a novel contact-biasing arrangement by which contact pressure may be adjusted with ease.

A further object of this invention is the provision of contact biasing arrangements in circuit breaker mechanisms, which biasing arrangements are simple in construction and in their ease of operation and by means of which the relative and absolute contact pressures of the main and arcing contacts may be adjusted.

A still further object of the invention is to provide a switch mechanism having a compact easily adjustable arrangement not only for the purpose of varying contact pressures, but also for inhibiting the tendency of the contacts to bounce or chatter.

By way of a brief summary of but one embodiment of this invention, I provide a circuit breaker in which a contact-carrying arm is movable through a short are toward and away from a stationary contact assembly. On the contact-carrying arm a pair of movable contact members are pivoted on a single axis. One of these pivotal contact members, the arcing contact, is longer than the other and is arranged to be the first to close and the last to open when the circuit breaker is actuated. Each one of the movable contact members on the contact-carrying arm is provided with an individually adjustable spring biasing arrangement which includes an inverted cup-shaped member mounted on the contact-carrying arm with its open mouth facing toward the respective contact memher. A helical spring contained within the recess of each cup-shaped member bears on the respective movable contact member below to exert a bias thereon in a direction tending to rotate it toward the stationary contact assembly. The opposite end of each helical spring bears, however, against an adjustable flanged member within the asso ciated cup-shaped recess which can be manipulated thruogh an opening provided in the base of the cup-shaped member to compress or expand the spring. In a preferred form of the invention, the flanged member comprises an elongated tubular stud which is dimensioned so as to provide a positive backstop for the movable contact to inhibit bouncing or chattering of the contact.

Further details of the invention as well as additional objects and advantages will be more readily perceived with reference to the following more complete description taken in connection with the accompanying drawings wherein:

FIGURE 1 is a side view of a circuit breaker assembly constructed in accordance with this invention showing the housing thereof broken away to reveal the contact structure of the switch mechanism;

FIGURE 2 is an enlarged view, partially in section, of the contact structure shown in FIGURE 1;

FIGURE 3 is a view similar to that of FIGURE 2 showing the contact structure in open-circuit position;

FIGURE 4 is a partial detail view of the FIGURE 2 construction illustrating one of the possible adjustments.

Turning now to FIGURE 1, therein is shown a circuit breaker having a housing 10 in which a toggle mechanism 11 illustrated generally in dotted lines is operated in response to movements of an operating handle 12 projecting through the top of the circuit breaker housing. The toggle mechanism may also be, and ordinarily is, actuated by an overload protective mechanism 13, also indicated generally in dotted lines, to trip the toggle mechanism from an ON condition to an OFF con-dition in response to electrical overloads. The toggle mechanism controls a switching assembly 14 revealed through the cutout portion in the side of the circuit breaker housing. Within any particular circuit breaker housing there may be from one to several such switching assemblies. For clarity, only one such switching assembly is shown in this and in succeeding illustrations. The purpose of the switching assembly shown is, of course, to open and close a circuit through the circuit breaker between a pair of terminal connections.

When the switching assembly is in its closed or ON condition as illustrated in FIGURE 1, circuit continuity can be traced from the terminal assembly 15 through the overload mechanism 13, through a connecting strip 17 to a pigtail cable 18 fastened at one of its ends to the connecting strip. The opposite end of the pigtail cable is jointed to a movable contact member 20, which has a contact surface 21 arranged thereon to engage another contact surface 22 on stationary contact assembly 23. From the stationary contact assembly 23, circuit continuity can be traced through another connecting strip 24 to terminal assembly 25.

An additional set of relatively movable electrical contacts is provided in parallel to those just described to function as arcing contacts. A movable arcing contact member 26 is connected through an additional pigtail cable to the connecting strip 17, although the latter cable is is not visible in FIGURE 1 because it is out of sight behind cable 18. The movable arcing contact has a contact surface 27 thereon which engages a stationary arcing contact surface 28 on the stationary contact assembly 23.

In the preferred embodiment illustrated, both the movable main contact 20 and the movable arcing contact 26 are pivoted on the same rod 3i) for limited movement about a single pivotal axis. The opposite ends of rod 3t) are fastened by staking or otherwise into the depending sides of an elongated channel-shaped contact-carrying arm 31. Contact-carrying arm 31 is itself pivoted at one end on a rod 32 mounted fixedly within the circuit breaker housing. It is to be noted that the other end of the contact-carrying arm '31 extends to a position adjacent and overlying the above-described electrical contact members. Through a mechanical link 33 to the toggle mechanism 11 the contact-carrying arm 31 is movable through a short arc about its own pivotal axis to carry with it the movable contacts 20 and 26.

On the compound movable contact assembly thus constructed there is provided in accordance with this inven tion an adjustable spring bias for each of the movable contacts by means of which the contact pressures of the main contact surfaces and the arcing contact surfaces may be adjusted. As seen in FIGURE 2, a helical bias spring 35 hearing at its lower end against a spring seat 36 on the main movable contact 20 tends to rotate the latter toward engagement with the stationary contact surface 22. The upper end of bias spring 35 nests within an inverted cupshaped member 37 fastened within the end of the contactcarrying member 31 which extends over the stationary contact surfaces.

An adjustable spring seat is provided for the upper end of the helical spring in the form of an internally threaded stud 38 having a flange 39 against which the spring 35 bears. This T-shaped stud, which extends downward inside the helical spring 35, is threaded onto a headed screw member 40 having an enlarged head resting at the inner extremity of the cup-shaped receess. The head of the screw member 40 may be reached for adjustment through an access aperture 41 provided for this purpose through the inner end or bottom of the inverted cup. The diameter of the access aperture is smaller than that of the screw head to trap the screw 40 and the flanged stud 38 within the recess. A similar adjustable spring biasing arrangement is provided for the arcing contacts by a spring 44- bearing against the movable arcing contact 26 at its lower end and at its other end against an identical adjustable spring seat in cup-shaped retainer 45. Rotation of the screw 40 counterclockwise causes it to thread outwardly of the stud 38, thereby forcing the stud 38 farther away from the closed end of the cup 37 and further compressing the spring 35. Rotation of the screw 40 in the opposite direction draws the stud 38 closer to the closed end of the cup 37 and lengthens the spring 35.

It can be seen therefore that the bias provided by springs 35 and 44 may be independently and easily adjusted by manipulation of the associated screw member through the access aperture provided in each cup-shaped retainer. The adjustments, once made, are maintained by friction between the respective screw-heads 4t) and the partial end wall of the cups 37 which prevents the studs from loosening through rotation. Under the urging of the bias springs described, the movable main and arcing contacts function in sequence. In moving from the ON or circuit closed position shown in FIGURE 2 to the OFF or circuit open position shown in FIGURE 3 the first contacts to separate are the main contact surfaces 21 and 22. Immediately thereafter arcing contact surfaces 27 and 28 separate and any are which occurs is struck between the latter contact surfaces instead of between the main contact surfaces. Those arcs formed between contact surfaces 27 and 28 are driven magnetically outward along the curved arcing surfaces 46 and 47 to protect the contact surfaces and to stretch and break the arc. When the contact-carrying arm reaches the top of its circuit-opening stroke as shown in FIGURE 3 and comes to rest against a stop member represented by element 48 the movable contacts Ztl and 26 are biased by their respective springs and 4 5 to extreme clockwise positions about rod 30. The movable contact members are restrained against further rotation by engagement between the inner surface of the contact-carrying arm 31 and stops 51 on the movable contact members.

When the contact-carrying arm is driven again to the ON or circuit closed position, the main and arcing contacts engage in the reverse order from which they separated. Thus contact surfaces 27 and 28 engage first, and main contact surfaces 21 and 22 thereafter.

It is important to prevent the contacts, and especially the arcing contacts, from bouncing upon closing. If they do bounce, arcing is likely to occur between the main contact surfaces, which could cause pitting of the contacts, and poor operation normally. In order to minimize contact bouncing, the length of the studs 38 is preferably selected to be such that when the contacts are in closed position and the spring 35 is adjusted to a desirable pressure, the end of the stud 38 is closely adjacent, but slightly spaced from, the contact 20. See FIGURE 4. Thus while resilience is provided for desired contact pressure, a close positive backstop is provided which greatly inhibits and virtually prevents contact bouncing.

It is thus evident that the adjustment features provided in the above-described circuit breaker assembly offer ease of adjustment and simplicity of construction and that they permit individual adjustment of respective contact pressures. While but one preferred embodiment of this invention has been shown and described, it will be obvious that various changes or modifications may be made in the structure without departing from the invention in its broader aspects. The concluding claims are therefore intended to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new an desire to secure by Letters Patent of the United States is:

1. An electrical switch mechanism comprising:

(a) a stationary contact;

(b) an elongated switch arm having one end pivoted and the other end extending into a position adjacent said stationary contact for movement toward and away from said stationary contact;

(c) a movable contact movably supported upon said switch arm;

(d) means for adjusting the contact pressure between said stationary and movable contacts when closed including means carried by said switch arm defining a cylindrical recess facing toward said movable contact;

(e) a stop member positioned in said recess, and extending substantially across the internal diameter of said recess;

(f) a compression spring hearing at one end against said stop member and at the other end against said movable contact;

(g) said recess-defining means having an access aperture therethrough extending into communication with the interior of said recess, and

(h) adjusting means in said recess arranged to be manipulated through said access aperture for varying the position of said stop member with said recess.

2. An electrical switch mechanism comprising:

(a) a stationary electrical contact;

(b) an elongated contact-carrying arm pivotally mounted for switch opening and switch closing movements;

(c) a movable electrical contact movably mounted on said contact-carrying arm for movement with said arm toward and away from said stationary contact, said stationary and movable contacts having surfaces thereof arranged to be mutually engaged upon switch closing movements of said contact-carrying arm;

(d) means for adjusting the contact pressure between said stationary and movable contacts including means carried by said contact-carrying arm defining a cupshaped recess facing toward said movable contact with an access aperture of reduced diameter extending into the innermost extremity of said cup-shaped recess;

(e) a threaded screw member positioned in said recess and having an enlarged head accessible through said access aperture, said head having a larger diameter than that of said access aperture;

(f) a threaded stop member engaged by said screw member within said recess and having a portion extending across the internal diameter of said recess, and

(h) a helical spring positioned in said recess, said spring bearing at one of its ends against said stop member and at the other of its ends against said movable contact to bias said movable contact in a direction tending to close said fixed and movable contacts, whereby the contact pressure between said fixed and movable contactsmay be varied by rotation of the head of said screw member through said access aperture.

3. An electrical switch mechanism comprising:

(a) a stationary contact;

(b) an elongated switch arm having one end pivoted and the other end extending into a position adjacent said stationary contact for movement toward and away from said stationary contact;

(c) a movable contact pivoted upon said switch arm said movable contact being positioned to engage said stationary contact upon movement of said switch arm toward said stationary contact;

(d) means for adjusting the contact pressure between said stationary and movable contacts including a cup-shaped member carried by the movable end of said switch arm defining a cylindrical recess facing toward said contact member, said cup-shaped member having an access aperture of reduced diameter communicating from the outside with the innermost end of said recess;

(e) a threaded screw member positioned in said recess and having an enlarged head operable through said access aperture, said head having a larger diameter than that of said access aperture;

(f) a threaded collar threadably engaged by said screw membetr within said recess and having a flange thereon extending across the internal diameter of said recess, and

(g) a helical spring positioned concentrically about said threaded collar, said spring bearing at one of its ends against the flange of said collar and at the other of its ends against said contact member to bias said contact member in a direction tending to close said contacts, whereby the contact pressure between said fixed and movable contacts may be varied by adjustment of the head of said screw member through said access aperture.

4. An electrical switch mechanism comprising:

(a) a stationary contact;

(b) an elongated switch arm having one end pivoted, the other end extending into a position adjacent said stationary contact for movement toward and away from said stationary contact;

(c) a movable contact pivoted upon said switch arm, said movable contact being positioned to engage said stationary contact upon movement of said switch arm toward said stationary contact;

(d) means for adjusting the contact pressure between said stationary and movable contacts including means carried by said switch arm defining a cylindrical recess facing toward said contact member;

(e) a headed screw member positioned in said recess with its head in the innermost end thereof;

(f) a threaded stud engaged by said screw member,

said stud having a flange thereon extending substantially across the internal diameter of said recess;

(g) a helical spring positioned coaxially about said stud and bearing at one end against said flange and at the other end against said movable contact to bias said movable contact toward said stationary contact, and

(h) said recess-defining means having an access aperture communicating with the head of said screw member, said access aperture being of smaller lateral dimensions than the head of said screw member, whereby the position of the flange within said cylindrical recess may be adjusted by manipulation of the head of said screw member through said access aperture.

5. An electric switch mechanism comprising:

(a) a stationary contact;

(b) a movable contact arm;

(c) a movable contact member carried by said movable contact arm and movable by said contact arm into and out of engagement with said stationary contact;

((1) a compression spring disposed and arranged between said movable contact member and said movable contact arm and urging said movable contact member away from said movable contact arm;

(e) means limiting movement of said movable contact member away from said movable contact arm;

(f) a cup-shaped retaining member carried by said movable contact arm and opening in the direction of said movable contact member and surrounding said compression spring;

(g) an adjustable stop member comprising an elongated generally tubular portion extending within said com pression spring and a circular flange portion at one end overlying the end of said compression spring;

(h) a headed adjusting screw threadedly engaged in said tubular portion of said stop member and having its head abutting against the closed end of said cup memher;

(i) said cup member having an aperture in said closed end affording access to said head of said screw, whereby said screw may be rotated to vary the position of said adjustable stop member axially along said screw, and

(j) the length of said tubular portion of said stop member being selected so that in said closed position of said contact arm the end of said tubular portion remote from said flange portion is disposed closely adjacent said movable contact member to substantially inhibit bouncing of said contact member when said contact member is moved into engagement with said stationary contact member.

6. An electric switch comprising:

(a) a stationary contact;

(b) an elongated contact arm pivotally supported in said circuit breaker adjacent one end thereof;

(0) a relatively movable contact pivotally supported on said contact arm at a point spaced from said pivotally supported end and movable by said contact arm into and out of engagement with said relatively stationary contact;

(d) a compression spring disposed and arranged to act between said contact arm and said movable contact member and urging said contact member away from said contact arm;

(e) means limiting movement of said contact member away from said contact arm;

(f) adjustable stop means for said compression spring comprising an inverted cup-shaped member carried by said contact arm and opening in the direction of said movable contact member, said compression spring extending within said cup-shaped member;

7 8 (g) an elongated generally tubular threaded stud withnot in contact With said movable contact member, In 881d pp member and eXtendlIlg Wlthln 831d whereby to substantially inhibit bouncing of said compression spring, said stud carrying a flange adjacent one end thereof acting as a stop for said compression spring; 5 (h) a headed screw threadedly engaged in said stud and having its head portion abutting against the incontact member When moved into engagement with said stationary contact member.

References Cited by the Examiner ner surface of the closed end of said cup-shaped UNITED STATES PATENTS member, said closed end of said cup-shaped member 2, 86 5/ 1943 Lindstrom 200-465 X having an opening therein aifording access there- 10 2,492,009 12/1949 a din 6t :11. 20039 X through to permit rotation of said screw to vary the v2,545,341 3/ 1951 Cazswell 200146 X axial position of said adjustable stop member there- 2,921,169 1/1960 Judd et al 200-146 X along;

(i) the length of said elongated threaded stud being KATHLEEN H. CLAFFY, Primary Examiner.

selected so that in the closed position of said contact 15 arm, the end of said stud extends closely adjacent but BERNARD GILHEANY Exammer' 

1. AN ELECTRICAL SWITCH MECHANISM COMPRISING: (A) A STATIONARY CONTACT; (B) AN ELONGATED SWITCH ARM HAVING ONE END PIVOTED AND THE OTHER END EXTENDING INTO A POSITION ADJACENT SAID STATIONARY CONTACT FOR MOVEMENT TOWARD AND AWAY FROM SAID STATIONARY CONTACT; (C) A MOVABLE CONTACT MOVABLY SUPPORTED UPON SAID SWITCH ARM; (D) MEANS FOR ADJUSTING THE CONTACT PRESSURE BETWEEN SAID STATIONARY AND MOVABLE CONTACTS WHEN CLOSED INCLUDING MEANS CARRIED BY SAID SWITCH ARM DEFINING A CYLINDRICAL RECESS FACING TOWARD SAID MOVABLE CONTACT; (E) A STOP MEMBER POSITIONED IN SAID RECESS, AND EXTENDING SUBSTANTIALLY ACROSS THE INTERNAL DIAMETER OF SAID RECESS; 